75 megahertz of 5.9 GHz spectrum are in play
This week U.S. Federal Communications Commission Chairman Ajit Pai laid out a plan to reallocate 75 megahertz of the 5.9 GHz band for cellular vehicle-to-everything (C-V2X) communications and for unlicensed uses like Wi-Fi. The FCC will vote on the notice of proposed rulemaking at its Dec. 12 meeting.
A favorable vote in December–which is very likely given support for the change among a majority of FCC commissioners, would also initiate a public comment period with a particular emphasis on potentially reserving 10 megahertz of the 75 megahertz for Dedicated Short-Range (DSRC). The 5.9 GHz band was initially set aside for DSRC, based on the IEEE 802.11p standards and meant for Intelligent Transportation Systems, never really caught on to any extent with Pai calling the technology a “promise unfulfilled” in comments made on Nov. 20 at the National Union Building in Washington D.C.
Pai’s plan calls for dividing up the 75 megahertz as follows: the lower 45 megahertz would go for unlicensed uses like Wi-Fi, the upper 20 megahertz for C-V2X, and the remaining 10 megahertz would be the subject of public comment on whether it should remain for DSRC or also go to C-V2X. It’s worth noting that the 45 megahertz that could go over to unlicensed use is adjacent to unlicensed spectrum in the 5.725 GHz to 5.850 GHz range.
On unlicensed uses like Wi-Fi, Pai also called out work to open up the 6 GHz band for unlicensed use. “We need to make more spectrum available for unlicensed use,” he said. “The FCC hears this call.” Regarding the 45 megahertz up for a vote next month, the “sub-band [is] ideally suited for unlicensed use. Thanks to its neighbor, this spectrum would punch above its weight. Having more contiguous spectrum here is essential for the larger channels needed to support innovative use cases.”
In the context of 5G, the 5 GHz and 6 GHz bands are the subject of 3GPP standardization work for what’s called New Radio-Unlicensed, or NR-U. Expected to be included in Release 16, NR-U considers operating cellular in unlicensed bands in a non-standalone mode of operation like LAA for 5G, or in a standalone mode akin to MulteFire for 5G.
For vehicular communications, C-V2X has been embraced by the telecom ecosystem as well as automotive manufacturers. Audio, BMW, Ford, Toyota and others automakers, along with dozens of global operators, have collaborated on C-V2X testing, which is also the subject of ongoing standardization work regarding an evolutionary path from LTE to 5G NR.
The 5G Automotive Association, a cross industry consortium, said of the FCC move, “Extensive crash avoidance testing continues to demonstrate that C-V2X technology will deliver safety benefits to the American Public. We look forward to working with all stakeholders throughout this process to ensure that spectrum regulations adequately address the needs of transportation safety.”
Dean Brenner, Qualcomm’s senior vice president of spectrum strategy and technology, called the FCC proposal “visionary” and said in a statement it “will enable us to bring the tremendous, unmatched safety benefits from C-V2X to U.S. drivers, passengers, and pedestrians. We look forward to working with the FCC and all other stakeholders to get C-V2X on the air as quickly and broadly as possible.”
DSRC vs. C-V2X
DSRC is is “a two-way short-to-medium-range wireless communications capability that permits very high data transmission critical in communications-based active safety applications,” according to the U.S. Department of Transportation’s Intelligent Transportation Systems Joint Program Office, which heads up much of the research related to DSRC.
In general, intelligent transportation systems — smarter infrastructure, as well as vehicles with new driver assistance and eventually, autonomous driving features — are seen as a way to reduce traffic accidents and fatalities, as well as improve traffic congestion and fuel efficiency.
The idea was (is?) to use DSRC for vehicle-to-vehicle and vehicle-to-infrastructure communications. The spectrum is seen as particularly useful for V2X communications because it can support very low-latency, secure transmissions, fast network acquisition and in general, the ability to handle rapid and frequent handovers that are inherent in a vehicle environment, as well as being highly robust in adverse weather conditions. ITS also notes that it is tolerant of multi-path transmission.
C-V2X considers direct communications between vehicles and infrastructure, pedestrians and other vehicles; and vehicle to network communications using traditional mobile networks deployed in licensed spectrum. The major benefits of connecting a vehicle to everything around it are non-line-of-sight sensing, improved situational awareness and conveying intent. Connectivity also enables new types of in-vehicle infotainment experiences and integration with other connected, cloud-based services, smart home applications for instance.
As Pai put it, “C-V2X would use standard cellular protocols to provide direct communications between vehicles, and, as the name suggests, everything—including other vehicles on the road, infrastructure (like light poles), cyclists (like me), pedestrians, and road workers. C-V2X is also expected to support new, advanced applications as we transition to faster, more responsive 5G networks. And it is backed by automakers like Ford, Audi, BMW, Daimler, and Tesla.”
C-V2X is a 5G “game-changer”
Brenner, in an interview with RCR Wireless News during Mobile World Congress Los Angeles, characterized C-V2X as one of five 5G game-changers alongside dynamic spectrum sharing, NR-U, small cells and enhanced millimeter wave transmissions.
He noted that, contained in the LTE specifications, is direct communications between vehicles and vehicles and infrastructure. On DSRC, “It really has not taken off in these 20 years. DSRC has really only been deployed in the most minimal way. We went back to the drawing board. A cars just another device and we’re putting a lot of smartphone functionality in cars. Why do we put this smartphone technology, just refine it, and put it in cars. There’s now a full spec for how cars can use 4G.”
“If DSRC was the best that could be done, we wouldn’t have done it. There are inherent advantages to cellular. Using cellular we’re going to get better range and better reliability. If I’m trying to communicate with cars as they go around a curve…or at night, or in a rainstorm, or in a snowstorm….The technology that’s more reliable, that has greater range, that’s going to translate into safety.”